A ship heels toward a side, when damage occurs at either of port and starboard side shells resulting in flooding of the hull. In this case, the ship is designed to have adequate stability that it can come to a safe equilibrium from the inclined state.
Such a ship is required to be capable of stable self-navigation to the nearest port after being damaged and flooded.
Patent Literature 1 discloses a configuration in which a compartment at the port side and a compartment at the starboard side of the hull are brought in connection with each other. According to the configuration, when a compartment of the two compartments is flooded, since water can be moved to a second compartment, the heeling of the hull can be reduced and stability can be increased.
Patent Literature 2 discloses a ship having a pair of ballast tanks separated in athwart ship direction, a connection pipe configured to bring the ballast tanks in connection with each other, and a valve configured to open and close the connection pipe. The ship disclosed in Patent Literature 2 is configured such that a valve is opened to move ballast water using potential energy when the heel of the hull exceeds a threshold and is closed when the heel of the hull is less than the threshold.